Mechanical resonators for standard frequency oscillators

ABSTRACT

A mechanical resonator comprising a primary vibrator having a spring member with two axes of symmetry at right angles and two vibration masses coupled to the spring member and arranged to vibrate in mutually opposite senses with the centers of vibration thereof arranged to move on a rectilinear path which coincides with one of said axes. An even number of pairs of secondary vibrators are carried by said primary vibrator with at least one pair of said secondary vibrators associated with each of said vibration masses of the primary vibrator. The centers of vibration of the two secondary vibrators which together form each pair are arranged to move with components of motion parallel to the said axis of symmetry coincident with the path of of the vibration masses of the primary vibration which are in the same sense, and with components of motion at right angles to this axis of symmetry which are mutually opposed.

United States Patent MECHANICAL RESONATORS FOR STANDARD FREQUENCY OSCILLATORS 18 Claims, 12 Drawing Figs.

11.8. CI 310/25, 58/23 Int. Cl. H02k 33/00 Field of Search 3 10/25, 21, 22, 15; 58/23, 23 A, 23 A0, 23 TF, 28; 331/116, 1 16 M Primary Examiner-D. F. Duggan Attorneywoodhams, Blanchard and Flynn ABSTRACT: A mechanical resonator comprising a primary vibrator having a spring member with two axes of symmetry at right angles and two vibration masses coupled to the spring member and arranged to vibrate in mutually opposite senses with the centers of vibration thereof arranged to move on a rectilinear path which coincides with one of said axes. An even number of pairs of secondary vibrators are carried by said primary vibrator with at least one pair of said secondary vibrators associated with each of said vibration masses of the primary vibrator. The centers of vibration of the two secondary vibrators which together form each pair are arranged to move with components of motion parallel to the said axis of symmetry coincident with the path of of the vibration masses of the primary vibration which are in the same sense, and with components of motion at right angles to this axis of symmetry which are mutually opposed.

PATENTED SEP28|971 SHEET 1 [IF 4 PATENTED SEPZBIQYI 3,609,419

SHEET 3 0F 4 amwmw "WW, KM 11% MECHANICAL RESONATORS FOR STANDARD FREQUENCY OSCILLATORS This invention relates to mechanical resonators for standard frequency oscillators, particularly in time-measuring instruments, such a resonator comprising a primary vibrator which includes a spring member with two axes of symmetry at right angles to each other and two vibration masses coupled to the spring member and arranged to vibrate in mutually opposite senses with the centers of vibration thereof arranged to move on a rectilinear path which coincides with one of the axes of symmetry.

Vibrators of this kind have been known in various forms for some time and are generally coupled to an electrical oscillator by electromechanical means, so that the vibration frequency of the oscillator conforms to the natural vibration frequency of the mechanical vibrator. Examples of vibrators of this type are to be found in Swiss patent specifications Nos. 406,984 and 414,768 and in US. Pat. No. 1,963,719. The fact that with these known vibrators the centers of vibration of the vibration masses move on a rectilinear path provides the advantage that the natural vibration frequency of the vibrator is unaffected by the influences of the gravitational field and thus does not depend upon the position and orientation of the vibrator in space. This makes this type of vibrator particularly interesting for use in portable instruments, such as wristwatches.

In the use of such vibrators the problem of finely tuning the vibration frequency often arises. Until now, it has been usual to carry out this tuning by removing, e.g. by filing away, material from those parts of the vibrator which act as stores of potential energy when the frequency is too high, and from those parts of the vibrator which act as stores of kinetic energy when the frequency is too low. Although this method appears quite feasible in production, it is complicated to carry out on the finished product if subsequent correction is necessitated by wear for example, and can then only be successfully carried out by specially qualified experts.

It is already known for vibrators wherein those parts acting as stores of kinetic energy move on curved paths to carry out fine tuning of the vibration frequency by providing the vibrator with pivotably mounted masses whose pivot axes do not pass through their centers of gravity. With curved paths which are not rectilinear, the moment of inertia cannot be equated directly with the masses carried by the vibrator. By displacing the pivotable masses it is thereby possible to alter the moment of inertia and thus the natural vibration frequency of the vibrator without adding or removing any mass. This method cannot generally be used in vibrators of the type first mentioned above because the parts thereof which preferably serve to store kinetic energy move on rectilinear paths.

Moreover, it has been known for a long time that the natural frequency of vibrators incorporating a spring member can be tuned by altering the spring characteristics of the spring member, for example by applying more or less tension to a wire. This method of fine tuning is only possible with certain forms of spring member and has the disadvantage that the points of securement of the spring member are not free of forces created by the vibration and therefore exert reaction forces on the vibrator, with the result that the quality factor of the vibrator and thus the frequency stability are impaired.

The present invention is concerned with the problem of producing a mechanical resonator of the generic type first mentioned above wherein fine tuning is possible without the necessity for adding or removing mass and without changing the spring characteristics of the spring member.

In accordance with the invention, there is provided a mechanical resonator comprising aprimary vibrator which includes a spring member with two axes of symmetry at right angles to each other and two vibration masses coupled to the spring member and arranged to vibrate in mutually opposite senses with the centers of vibration thereof arranged to move on a rectilinear path which coincides with one of said axes of symmetry, and an even number of pairs of secondary vibrators carried by said primary vibrator with at least one pair of said secondary vibrators associated with each of said vibration masses of the primary vibrator, the centers of vibration of the two secondary vibrators which together form each pair being arranged to move with components of motion parallel to the said axis of symmetry coincident with the path of movement of the vibration masses of the primary vibration which are in the same sense, and with components of motion at right angles to this axis of symmetry which are mutually opposed, and the position of at least one part of each secondary vibrator being adjustable with respect to the primary vibrator to vary the resultant vibration frequency of the resonator.

Each secondary vibrator preferably comprises a bar-spring element which is secured at one end to the primary vibrator and at the other end is free. The free end of each bar-spring element may carry one or more terminating masses. Fine tuning of the vibration frequency of the resonator can be effected by moving the terminating masses along the longitudinal axis or axes of the bar-spring elements and/or by pivoting the barspring elements relative to the primary vibrator. In the latter case, one end of the bar-spring element of each secondary vibrator may be secured to a support member which is rotatably connected to the primary vibrator for movement about a pivotal axis perpendicular or parallel to the plane containing the axes of symmetry of the primary vibrator and which remains in any set position. It is furthermore possible to adjustably connect the bar-spring element of each secondary vibrator to a support member for longitudinal movement, the support member being fixedly or rotatably mounted on the primary vibrator, and the free end portions of the bar-spring elements being provided with or without additional masses. In another embodiment, a mass can be pivotably connected to the bar-spring element of each secondary vibrator by means of a pivot pin positioned eccentrically of the center of gravity of the mass so that the mass can be pivoted in relation to the barspring element for fine turning of the vibration frequency of the resonator, and then remains in this set position.

In order that the invention may be fully understood, a number of embodiments of mechanical resonator in accordance with the invention will now be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is an axomometric view of a first embodiment of resonator according to the invention;

FIG. 2 is a plan view of the resonator of FIG. 1;

FIG. 3 is a view of the resonator as observed along the line of the axis A and looking towards the resonator;

FIG. 3a is a cross-sectional view taken as along the axis A of FIG. 2 but through a slightly modified embodiment of resonator;

FIG. 4 is a plan view of a single pair of secondary vibrators of the resonator shown in FIGS. 1 to 3;

FIG. 5 is a similar view of a modified form of the pair of secondary vibrators; and

FIGS. 6 to 11 are plan views each of a modified single pair of secondary vibrators.

The mechanical resonator shown in FIGS. 1 to 3 comprises a primary vibrator ll, 12 which consists of a ring-form spring member 11 and two vibration masses 12 secured thereto. The primary vibrator 11, 12 has two axes of symmetry A and B which extend at right angles to each other. A crosspiece 13 extending along the axis of symmetry B serves to secure the spring member 11 to a base (not shown). The two vibration masses 12 are arranged opposite each other so that their centers of gravity lie on the other axis of symmetry A. Upon actuation of the primary vibrator, the masses l2 vibrate to and fro in opposite senses in such manner that their centers of gravity move on a rectilinear path which coincides with the axis of symmetry A. The spring member It thus undergoes flexing oscillations. In order that such mechanical oscillations should cause no tensile or compressive forces to be exerted on the crosspiece 13, the spring ring 11 has the shape shown in FIGS. 1 and 2 with alternately concave and convex portions.

The ends of the crosspiece 13 are each attached to the center of a convex ring portion, whilst the vibration masses 12 are each rigidly connected to an outwardly projecting tongue 14 at the center of a concave ring portion. This vibrator is known and is described for example in Swiss patent specifications Nos. 414,768 and 450,295.

Each projecting tongue 14 of the spring member 11 carries a pin-type support 1, 1' which has a pair of secondary vibrators 2, 3 and 2', 3' respectively mounted thereon. Each vibration mass 12 of the primary vibrator is associated with a pair of these secondary vibrators 2, 3 or 2', 3'. The pin-type supports 1, 1' are each rotatable about an axis c, c which is perpendicular to the plane containing the axes of symmetry A and B, as shown in FIGS. 1 and 3. The secondary vibrators carried by the support 1 each consist of a bar-spring element 2 and a terminating mass 3. One end of the bar-spring element 2 is inserted radially into the support pin 1 so that the longitudinal axis of the bar-spring element 2 extends parallel to the plane containing the axes of symmetry A and B. The mass 3 is carried at the free end of the bar-spring element 2. The two barspring elements 2 which comprise one pair of the secondary vibrators are arranged coaxially and are of the same length. They may be formed from a continuous bar of material which is secured at its center in the support pin 1. Similarly, the two end masses 3 are of the same size and at the same distance away from the axis of rotation c of the support pin. The pair of secondary vibrators carried by the support pin 1' and consisting of the bar-spring element 2 and the end masses 3' is constructed and arranged in a completely symmetrical manner.

To explain the manner of operation of the resonator and the fine adjustment of its vibration frequency reference is now made to FIG. 4 which shows one pair of secondary vibrators 2, 3 on a larger scale. The support pin 1 has here been rotated about the axis so that the longitudinal axis of the bar-spring elements 2 lies at an angle a to an axis b which extends parallel to the axis of symmetry B and cuts the axis of rotation c. In FIG. 1, the axis b and its counterpart b on the opposite side of the resonator are both indicated. If the vibration masses 12 of the primary vibrator 11, 12 vibrate in opposite directions, the support pin 1 likewise moves to and fro along the axis A. Thus, the secondary vibrators 2, 3 are stimulated to vibrate in a mode which is composed partly of bending vibrations and partly of longitudinal vibrations of the bar-spring elements 2.

The motion of each end mass 3 can be divided into two components which are respectively parallel to the axes of symmetry A and B. The components of this motion which are parallel to the axis of symmetry A and to the direction of movement of the support pin 1 are directed in the same sense, i.e. are additive, for the two end masses 3 of the particular pair of secondary vibrators, while the components of motion of the same end masses 3 parallel to the axis of symmetry B and to the axis b are opposed to each other. The former components of motion thus have an additive effect on the movement of the adjacent vibration mass 12 of the primary vibrator. The latter components of motion on the other hand cancel each other out in their effect on the primary vibrator.

It is obvious that by rotating the support pin 1 about its axis c, i.e. by altering the angle a, the relationship between the components of motion of the end masses 3 can be altered to thereby cause a corresponding change in the forces exerted by the pair of secondary vibrators on the adjacent primary vibration mass 12. If the natural vibration-frequency of the secondary vibrators 2, 3 is chosen so as to be lower than the original natural vibration frequency of the primary vibrator, the resultant vibration frequency of the resonator decreases with increasing angle a. If, on the other hand, the natural vibration frequency of the secondary vibrators is chosen so as to be higher than the original natural vibration frequency of the primary vibrator, an increase in the angle 0: results in an increase in the resultant vibration frequency of the resonator. Use is thereby made of the fact that the natural frequency of the longitudinal vibrations of the bar-spring elements 2 is higher than the natural frequency of the bending vibrations. In both cases,

it is preferable to arrange that the bar-spring elements 2, for a correctly tuned resonator, lie at a considerable angle a to the axis b, so that when finely adjusting the vibration frequency of the resonator, as subsequently becomes necessary, an alteration of the frequency either up and down is possible simply by rotating the pair of secondary vibrators about the axis 0 in one sense or the other. In order to maintain the dynamic symmetry of the resonator with respect to the axis of symmetry B, it is advisable to rotate each of the two support pins 1 and 1' by about the same angular amount so that the bar-spring elements 2' lie at about the same angle a to the axis b as the barspring elements 2 lie in relation to the axis b.

The modified embodiment illustrated in FIG. 3a only differs from the embodiment described above in that each projecting tongue 14 of the spring member 11 has two pairs of secondary vibrators associated therewith which are located symmetrically on opposite sides of the plane containing the axes of symmetry A and B of the primary vibrator. The support pins 1 and 1' are therefore longer and are mounted so that they project equally from the two sides of the said plane. Each projecting portion of the support pins 1, 1' bears a pair of secondary vibrators of the type described above.

The further embodiments described hereinafter and with reference to FIGS. 5 to 11 only differ from the first embodiment in the construction and/or arrangement of the secondary vibrators. It should be noted that in the case of each of the following modified constructions or arrangements of secondary vibrators, the latter may be provided either on one side or on both sides of the plane containing the axes of symmetry A and B of the primary vibrator, in the latter case in a manner similar to that shown in FIG. 3a.

As shown in FIG. 5, two rectilinear bar-spring elements 2 of equal length are clamped coaxially in a common support pin 1. In distinction from the first embodiment, the ends of the bar-spring elements 2 remote from the support pin I carry no terminating masses. The mass of each secondary vibrator thus consists only of the distributed mass of the bar-spring elements 2. In this case, as is well known, all the points of mass of a barspring element 2 can be concentrated into a single point which is referred to as the center of vibration. The same considerations apply to the movement of the center of vibration of the secondary vibrator as were mentioned above with reference to the centers of gravity of the end masses 3. The components of motion parallel to the axis of symmetry A and to the path of motion of the primary vibration masses are directed in the same sense, whilst the components of motion parallel to the other axis of symmetry B and to the axis b are opposed to each other. Tuning of the vibration frequency of the resonator is effected by altering the angle a, i.e. by rotating the support pin 1.

In the embodiment shown in FIG. 6, each secondary vibrator has its own support pin 1 which if rotatably connected to the spring member of the primary vibrator. The two support pins of the secondary vibrators which together form a pair are arranged at the same distance d along the axis b on respective opposite sides of the axis of symmetry A which coincides with the path of motion of the primary vibration masses. The secondary vibrators each consist of a bar-spring element 2 and a tenninating mass 3, the bar-spring element being radially secured at its one end in the associated support pin 1 and carrying the mass 3 at its other end. The two secondary vibrators which together form a pair are constructed and arranged in mirror image form with respect to the axis of symmetry A, not only with regard to their geometric configuration but also in respect of the spring characteristics and the masses. In order to tune the vibration frequency of the resonator, the two support pins 1 are rotated in opposite senses through approximately the same angle so that the angles a which the barspring elements 2 make with the axis b are altered. The mode of operation of these secondary vibrators is basically the same as described above for the first embodiment.

In the embodiment illustrated in FIG. 7, the secondary vibrators again each consist of a bar-spring.element 2 and a mass 3. The two bar-spring elements 2 of the secondary vibrators which together form a pair are arranged coaxially with respect to each other and each have one end mounted in a common support-member 1 which, in contrast to the embodiments described heretofore, is fixedly and not rotatably connected to the spring member of the primary vibrator. The longitudinal axis of the bar-spring elements 2 extends along the axis b at right angles to the axis of symmetry A and to the path of motion of the primary vibration masses. In order to enable the vibration frequency the resonator to be tuned, the end masses 3 are displaceable in the longitudinal direction of the bar-spring elements 2. For this purpose, each of the end masses 3 is slidably mounted on its associated bar-spring element and is held in an adjusted position by static friction. If the resonator vibrates, the end masses 3 execute additional vibratory movements on arcuate paths which are centered on the center of the support member 1. The components of movement of the end masses 3 parallel to the axis A are in the same sense and effect the vibration frequency of the resonator, whereas the components of movement parallel to the axis 1: are in opposite senses and have no net effect. In order to tune the vibration frequency of the resonator, the spacings of the two end masses 3 from the support member I are altered at least approximately symmetrically to thereby cause an alteran'on of the natural vibration frequency of the secondary vibrators.

The embodiment shown in FIG. 8 only difiers from the example last described above in that the two bar-spring elements 2 of the secondary vibrators which together form a pair are not mounted coaxially in the support member I but at an angle to each other. The support member 1 is, however, again rigidly connected to the spring member of the primary vibrator. The longitudinal axes of the two bar-spring elements 2 each lie at the same angle a to the axis b. Tuning of the vibration frequency of the resonator is again efiected by moving the masses 3 along the bar-spring elements 2.

In a modification of the embodiments shown in FIGS. 7 and 8 but which is not however shown in the drawings, the masses 3 are fixedly, i.e. nondisplaceably, mounted on the end portions of the bar-spring elements 2 remote from each other, but the adjacent end portions of the bar-spring elements are adjustably held by the support member 1 so that the free length of each bar-spring element can be altered in order to produce the desired tuning of the resonator. With this variant the masses 3 can be dispensed with if desired, and, as in the embodiment of FIG. 5, the distributed masses of the bar-spring elements 2 can be used alone.

In the embodiment illustrated in FIG. 9, two support members l are arranged at equal distances along the axis b on respective opposite sides of the axis of symmetry A and are rigidly connected to the primary vibrator. A rectilinear barspring elements 2 like a cord is held between the two support members i with the ends of the spring element secured to the support members 1. Two masses 3 are slidably movable on the respective bar-spring elements 2 and will remain in a set position, for example by static friction. Again, a pair of secondary vibrators are used which each consist of a half of the barspring element 2 and one of the masses 3. One can consider these secondary vibrators to be developed from the embodiment of vibrator shown in FIG. 7 if the latter were cut in two along the axis A and the two halves were each turned through 180 so that the hitherto free ends of the bar-spring element faced each other and could even be joined together. To alter the natural vibration frequency of the pair of secondary vibrators of FIG. 9, and thus the vibration frequency of the resonator, the two masses 3 are moved along the bar-spring element 2, it being noted that the spacing d of each of the masses 3 from the axis of symmetry A is at least approximately the same.

FIG. 10 illustrates an embodiment wherein the secondary vibrators 2, 3 are both fixedly held by a common support member I which rigidly connected to the primary vibrator. The secondary vibrators comprise coaxially arranged barspring elements 2 which are each secured at their one end in a support member 1. The free end portions of the bar-spring elements 2 each carry a mass 3 which is pivotably connected to the associated spring element by means of a pivot pin 5, positioned eccentrically of the center of gravity of the mass and which is arranged to remain in any adjusted pivoted position. The pivot pins 5 are located at equal distances from the axis of symmetry A on opposite sides thereof. By pivoting the masses 3 through an angle a relative to the axis b which coincides with the longitudinal axis of the bar-spring elements 2, the natural vibration frequency of the secondary vibrators, and thus the vibration frequency of the resonator, is altered. For reasons of symmetry, one endeavors to pivot the two masses 3 through the same angle.

The embodiment illustrated in FIG. 11 is similar to that shown in FIG. 7, but the end masses 3 are here difierently ar ranged so as to be adjustable on the bar-spring elements 2. The latter each have at their outer end an enlargement 4 provided with an external thread. The end masses 3 are formed as correspondingly threaded nuts which are screwed on to the enlargements 4. Tuning of the vibration frequency of the resonator is effected by rotating the end mass 3 on their enlargements 4 whereby the masses are displaced along the longitudinal axis of the bar-spring elements 2.

In the preceding description of the various embodiments, the secondary vibrators which together form a pair are always arranged so that the oppositely directed components of motion of the center of vibration are parallel to the axis of symmetry B (see FIGS. 1 and 2). From spatial considerations this solution will be the most advantageous in most cases, because then the longitudinal axis or axes of the bar-spring elements 2 extend parallel to the plane which contains the axes of symmetry A and B and in which for the most part the spring member 11 also lies. However, it is equally possible to orientate the pair of secondary vibrators in another direction on the spring member of the primary vibrator, if only the mutually opposed components of motion of the end masses 3, or of the centers of vibration of the pair of secondary vibrators, are at right angles to the axis of symmetry A and are mutually cancelling. Thus for example in FIG. 1, the arrangement could be so modified that the axes of rotation c, c' of the support pins 1 and 1' coincide respectively with the axes b and b, and the bar-spring elements 2 project on opposite sides of the plane containing the axes of symmetry A and B, e.g. upwards and downwards instead of to the left and right.

It is also possible, and in certain cases preferable, to combine pivotability of the bar-spring elements with adjustability of the masses carried thereby, for example in such manner that in the embodiments of FIGS. 4 and 6, the masses 3 are arranged to be displaceable on the bar-spring elements 2, possibly in a similar manner to that shown in FIGS. 7, 10 or 1 1 It may be advantageous to manufacture the bar-spring elements of the secondary vibrators from a specially suitable material whose changes in length in response to changes in the ambient temperature cause a change in the natural vibration frequency of the secondary vibrators which counteracts temperature-responsive changes in the natural vibration frequency of the primary vibrator, so that the resultant vibration frequency of the combined resonator is or is at least substantially independent of temperature.

However, the main advantage of the resonator of the present invention is that its vibration frequency can be finely tuned without mass having to be added or removed at any place. This advantage results in economic savings in the production of instruments or devices incorporating the resonator since tuning can be carried out more quickly and by less skilled personnel. Furthermore, there is practically no waste from inappropriate filing away of material. Since tuning can be repeated as often as desired, an important advantage of the resonator lies in the possibility of easy retuning if displace ment of the vibration frequency of the resonator arises, e.g. through wear or other factors. The tuning and retuning can also be carried out by relatively unskilled persons.

- vibrate in mutually opposite senses with the centers of vibration thereof arranged to move on a rectilinear path which coincides with one of said axes of symmetry; and an even number of pairs of secondary vibrators carried by said primary vibrator with at least one pair of said secondary vibrators associated with each of said vibration masses of the primary vibrator, the centers of vibration of the two secondary vibrators which together form each pair being arranged to move with components of motion parallel to the said axis of symmetry coincident with the path of movement of the vibration masses of the primary vibrator which are in the same sense, and with components of motion at right angles to this axis of symmetry which are mutually opposed, and the position of at least one part of each secondary vibrator being adjustable with respect to the primary vibrator to vary the resultant vibration frequency of the resonator.

2. A resonator according to claim 1, wherein each secondary vibrator comprises a bar-spring element which is secured at its end to the primary vibrator and is free at its other end.

3. A resonator according to claim 2, wherein the free end of each bar-spring element carries at least one mass.

4. A resonator according to claim 3, wherein said mass is displaceable along the longitudinal axis of the bar-spring element.

5. A resonator according to claim 3, wherein said mass and a part of the bar-spring element have engaging threads.

6. A resonator according to claim 3, wherein said mass is slidable on the bar-spring element and is held in position by static friction.

7. A resonator according to claim 3, wherein said mass is pivotably connected to the bar-spring element by means of a pivot pin positioned eccentrically of the center of gravity of the mass and is adaptcd to remain in any set pivotal position.

8. A resonator according to claim 2 wherein each bar-spring element is secured to a support member secured to the primary vibrator and is arranged to be displaceable along its longitudinal axis.

9. A resonator according to claim 2 wherein each two secondary vibrators which together form a pair comprise two coaxially arranged bar-spring elements having their adjoining ends connected to a common support member secured to the primary vibrator.

10. A resonator according to claim 2, wherein each two ,8 secondary vibrators which together form a pair comprise two bar-spring elements respectively located on opposite sides of the path of movement of the primary vibration masses and symmetrically disposed with respect to said path.

1 l. A resonator according to claim 2 wherein each secondary vibrator is rotatable relative to the primary vibrator about an axis perpendicular to the path of movement of the vibration masses of the primary vibrator and is adapted to remain in any set position.

12. A resonator according to claim 2, wherein one end of the bar-spring element of each secondary vibrator is secured in a support member which is rotatably connected to the primary vibrator for rotation about an axis perpendicular to the path of movement of the primary vibration masses and adapted to remain in any set position.

13. A resonator according to claim 9, wherein the common support member is rotatably connected to the primary vibrator for movement about a common pivot axis perpendicular to the path of movement of the primary vibration masses and is adapted to remain in any set position.

14. A resonator according to claim 13, wherein the two coaxial bar-spring elements are of the same length and the common pivot cuts the path of movement of the primary vibration masses.

15. A resonator according to claim 10, wherein each of the symmetrically disposed bar-spring elements of the secondary vibrators which together form a pair is mounted on its own support member which is rotatably connected to the primary vibrator for rotation about an axis perpendicular to the path of movement of the primary vibration masses and is adapted to remain in any set position, and said support members being rotatable about respective separate axes which are at equal distances from the path of motion of the primary vibration masses.

16. A resonator according to claim 1, wherein the natural vibration frequencies of the secondary vibrators are different from the natural vibration frequency of the primary vibrator.

17. A resonator according to claim 1, wherein the secondary vibrators each have at least one portion whose dimension alter in dependence on the ambient temperature to thereby create changes in the natural frequency of the secondary vibrator which counteract temperature responsive changes in the natural vibration frequency of the primary vibrator.

18. A resonator according to claim 17, wherein each secondary vibrator comprises a bar-spring element which is secured at its one end to the primary vibrator and is free at its other end, and wherein the bar-spring element of each secondary vibrator is the portion thereof which alters with changes in temperature. 

1. A mechanical resonator for standard frequency oscillators, particularly in time-measuring instruments, comprising a primary vibrator Which includes a spring member with two axes of symmetry at right angles to each other and two vibration masses coupled to the spring member and arranged to vibrate in mutually opposite senses with the centers of vibration thereof arranged to move on a rectilinear path which coincides with one of said axes of symmetry, and an even number of pairs of secondary vibrators carried by said primary vibrator with at least one pair of said secondary vibrators associated with each of said vibration masses of the primary vibrator, the centers of vibration of the two secondary vibrators which together form each pair being arranged to move with components of motion parallel to the said axis of symmetry coincident with the path of movement of the vibration masses of the primary vibrator which are in the same sense, and with components of motion at right angles to this axis of symmetry which are mutually opposed, and the position of at least one part of each secondary vibrator being adjustable with respect to the primary vibrator to vary the resultant vibration frequency of the resonator.
 2. A resonator according to claim 1, wherein each secondary vibrator comprises a bar-spring element which is secured at its one end to the primary vibrator and is free at its other end.
 3. A resonator according to claim 2, wherein the free end of each bar-spring element carries at least one mass.
 4. A resonator according to claim 3, wherein said mass is displaceable along the longitudinal axis of the bar-spring element.
 5. A resonator according to claim 3, wherein said mass and a part of the bar-spring element have engaging threads.
 6. A resonator according to claim 3, wherein said mass is slidable on the bar-spring element and is held in position by static friction.
 7. A resonator according to claim 3, wherein said mass is pivotably connected to the bar-spring element by means of a pivot pin positioned eccentrically of the center of gravity of the mass and is adapted to remain in any set pivotal position.
 8. A resonator according to claim 2, wherein each bar-spring element is secured to a support member secured to the primary vibrator and is arranged to be displaceable along its longitudinal axis.
 9. A resonator according to claim 2, wherein each two secondary vibrators which together form a pair comprise two coaxially arranged bar-spring elements having their adjoining ends connected to a common support member secured to the primary vibrator.
 10. A resonator according to claim 2, wherein each two secondary vibrators which together form a pair comprise two bar-spring elements respectively located on opposite sides of the path of movement of the primary vibration masses and symmetrically disposed with respect to said path.
 11. A resonator according to claim 2, wherein each secondary vibrator is rotatable relative to the primary vibrator about an axis perpendicular to the path of movement of the vibration masses of the primary vibrator and is adapted to remain in any set position.
 12. A resonator according to claim 2, wherein one end of the bar-spring element of each secondary vibrator is secured in a support member which is rotatably connected to the primary vibrator for rotation about an axis perpendicular to the path of movement of the primary vibration masses and adapted to remain in any set position.
 13. A resonator according to claim 9, wherein the common support member is rotatably connected to the primary vibrator for movement about a common pivot axis perpendicular to the path of movement of the primary vibration masses and is adapted to remain in any set position.
 14. A resonator according to claim 13, wherein the two coaxial bar-spring elements are of the same length and the common pivot cuts the path of movement of the primary vibration masses.
 15. A resonator according to claim 10, wherein each of the symmetrically disposed bar-spring elements of the secondary vibrators which together form a pair is mounted on its own support member which is rotatably connecTed to the primary vibrator for rotation about an axis perpendicular to the path of movement of the primary vibration masses and is adapted to remain in any set position, and said support members being rotatable about respective separate axes which are at equal distances from the path of motion of the primary vibration masses.
 16. A resonator according to claim 1, wherein the natural vibration frequencies of the secondary vibrators are different from the natural vibration frequency of the primary vibrator.
 17. A resonator according to claim 1, wherein the secondary vibrators each have at least one portion whose dimension alter in dependence on the ambient temperature to thereby create changes in the natural frequency of the secondary vibrator which counteract temperature responsive changes in the natural vibration frequency of the primary vibrator.
 18. A resonator according to claim 17, wherein each secondary vibrator comprises a bar-spring element which is secured at its one end to the primary vibrator and is free at its other end, and wherein the bar-spring element of each secondary vibrator is the portion thereof which alters with changes in temperature. 